PATHOGENESIS AND TREATMENT OF APLASTIC ANEMIA

再生障碍性贫血的发病机制和治疗

• 批准号: 6432684
• 负责人: NEAL S YOUNG
• 金额: --
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6432684
• 关键词: aplastic anemia; artificial immunosuppression; autoimmune disorder; bone marrow disorder; clinical research; cytotoxic T lymphocyte; gene targeting; hematopoiesis; hematopoietic stem cells; hepatitis; histocompatibility typing; human subject; human therapy evaluation; immunohematology; lymphokines; paroxysmal nocturnal hemoglobinuria; phosphatidylinositols; tissue /cell culture

Aplastic anemia (AA) and other types of bone marrow failure have clinical and laboratory features consistent with an autoimmune pathophysiology, with a diversity of inciting antigens, including viruses, chemicals, and drugs. Whatever its specific etiology, a majority of patients respond with hematologic improvement after immunosuppressive therapies. One important clinical feature of AA is its evolution, sometimes years after normalization of blood counts, to other hematologic diseases such as paroxysmal nocturnal hemoglobinuria (PNH), which derive from clones of hematopoietic stem cells. Our laboratory studies have focused on the immune pathophysiology of AA, identification of a viral antigen, and the mechanism of late clonal evolution. Studies of etiology have continued to focus on an unknown hepatitis virus in the post-hepatitis AA syndrome (see Z01 HL 02319-14 HB). Current studies of the immune systems role in bone marrow suppression have focused on gamma-interferon (gamma-IFN), a lymphokine that inhibits hematopoiesis in vitro and in vivo. In our animal model for immune-mediated AA, congenic lymphocytes induce profound marrow aplasia, which can be abrogated by early administration of anti- lymphocyte globulin (ATG), cyclosporine, and monoclonal antibody to gamma-IFN. Current efforts are directed to producing chronic aplasia by periodic infusions of lymphoid cells, as well as determination of the specificity of the immune response. We have measured gamma-IFN in circulating and marrow lymphocytes using flow cytometry. About 2/3 of patients with severe AA and also with the diagnosis of hypocellular myelodysplasia shown the presence of this cytokine in blood T cells; less than 10% of recovered patients scored positive. The presence of the cytokine was highly predictive for response to immunosuppressive therapies: 16/16 patients whose cells contained gamma-IFN responded, compared to 4/12 patients whose blood lacked gamma-IFN; IFN declined after treatment, while IL-4 content increased. Recurrence of IFN intracellularly predicted relapse. Marrow intracellular IFN may be even better correlated with response. Measurement of surface gamma-IFN allows isolation of viable activated T cells, which may be useful in determining lymphoid clonality and characterizing and even identifying their antigens. Intracellular cytokine measurements indicating TH1/TH2 balance are also altered by in vitro treatment with cyclosporine, various androgen preparations, and growth factor combinations; stem cell factor and granulocyte colony stimulating factor also depress IFN expression in vivo in normal individuals undergoing stem cell mobilization. In other clinical studies in aplastic anemia, 24 patients with newly diagnosed severe aplastic anemia have now been randomized in a comparative protocol; the response rate has been higher for ATG than for high dose cyclophosphamide, but frank relapses and cytogenetic abnormalities have occurred only in the ATG arm. For children, our standard protocol has been modified to shorten the duration of cyclosporine therapy, begin cyclosporine is begun later in order to avoid abrogation of ATG tolerization, and the new immunosuppressive agent mycophenolate mofetil has been added, all in an effort to decrease the high relapse rate. In the laboratory, late clonal disease, both PNH and myelodysplasia, using sensitive flow cytometric and fluorescent in situ hybridization assays. Approximately 20% of patients with AA and probably a larger proportion of cases of hypocellular myelodysplasia present with evidence of a PNH clone. Our results are consistent with the hypothesis that PNH represents an escape mechanism in immune-mediated bone marrow failure, and that two steps are required for the development of PNH. Alternatively, a glycosylphosphoinositol- linked protein may be involved in the initial antigenic stimulation. - autoimmunity, T cells, bone marrow failure, myelodsyplasia, immunosuppression, interferon - Human Subjects

性障碍性贫血（AA）和其他类型的骨髓衰竭具有临床和实验室特征，与自身免疫性病理生理学一致，煽动抗原，包括病毒，化学物质和药物。无论其具体的病因如何，大多数患者在免疫抑制疗法后会以血液学改善反应。 AA的一个重要临床特征是其进化，有时是在血液计数归一化后数年，这些血液学疾病（例如阵发性夜间血红蛋白尿症（PNH））源自造血干细胞的克隆。我们的实验室研究集中在AA的免疫病理生理学，病毒抗原的鉴定以及后期克隆进化的机制上。病因的研究继续关注肝炎后肝炎综合征中未知的肝炎病毒（请参阅Z01 HL 02319-14 HB）。当前对免疫系统在骨髓抑制中的作用的研究集中在γ-互化（Gamma-IFN）上，这是一种在体外和体内抑制造血的淋巴细胞因素。在我们的免疫介导的AA的动物模型中，先天性淋巴细胞会引起深刻的并且从抗杀菌细胞球蛋白（ATG），环孢菌素和单克隆抗体对Gamma-IFN的早期施用可以消除。当前的努力是通过周期性输注淋巴样细胞以及确定免疫反应的特异性来产生慢性植物的。我们已经使用流式细胞仪测量了循环和骨髓淋巴细胞的γ-IFN。大约有2/3的严重AA患者以及诊断出低细胞骨髓增生的患者，表明该细胞因子在血液T细胞中存在。不到10％的康复患者得分阳性。细胞因子的存在是对免疫抑制疗法反应的高度预测：16/16例，其细胞含有γ-IFN的患者反应，而血液缺乏血液缺乏γ-IFN的患者则反应。治疗后IFN下降，而IL-4含量增加。 IFN细胞内预测复发的复发。骨髓内IFN可能会更好地与响应相关。表面γ-IFN的测量允许分离活激活的T细胞，这可能有助于确定淋巴的克隆性和表征甚至鉴定其抗原。细胞内细胞因子测量表明TH1/TH2平衡也通过环孢霉素，各种雄激素制剂和生长因子组合的体外治疗也改变了；干细胞因子和粒细胞集落刺激因子还会在接受干细胞动员的正常个体中降低体内IFN表达。在其他性障碍性贫血的其他临床研究中，现已在比较方案中随机分配了24例新诊断的严重性性贫血患者。 ATG的反应率高于高剂量环磷酰胺，但是坦率的复发和细胞遗传学异常仅发生在ATG组中。对于儿童而言，我们的标准方案已经过修改以缩短环孢菌素治疗的持续时间，以避免消除ATG耐受性，开始了开启环孢素，并且已经添加了新的免疫抑制剂霉菌甲基甲酸甲酸甲酸酯小甲酸甲酸酯，所有这些努力都降低了高复发率。在实验室中，使用敏感的流式细胞仪和原位杂交测定法，晚期克隆疾病，PNH和骨髓增生性疾病。大约有20％的AA患者，可能会有较大的骨髓发育不良病例，并带有PNH克隆的证据。我们的结果与PNH代表免疫介导的骨髓衰竭的逃生机制的假设是一致的，并且PNH的发展需要两个步骤。或者，糖基磷酸肌醇链接的蛋白可能参与初始抗原刺激。 - 自身免疫性，T细胞，骨髓衰竭，骨髓增生，免疫抑制，干扰素 - 人类受试者